Find the Differential of the Function at the Indicated Number $$f ( x ) = \sqrt { x ^ { 2 } + 7 } ; \quad x = 3$$

Multiple Choice

Find the differential of the function at the indicated number.
Select the correct answer.
$$f ( x ) = \sqrt { x ^ { 2 } + 7 } ; \quad x = 3$$

A) $\frac { 3 } { 8 } d x$
B) $\frac { 3 } { 4 } d x$
C) $\frac { 3 } { 2 } d x$
D) $\frac { 1 } { 8 } d x$